Mistaken for Strangers, the documentary that opened this year’s Tribeca Film Festival, would make an uncannily excellent double feature with Sarah Polley’s Stories We Tell, slated for release in New York on May 10. Both films are documentaries about families (though Polley’s family history is considerably more fraught than director Tom Berninger’s appears to be), and both place the act of documenting, of filmmaking, at the forefront. The audience can never forget, while watching these films, that they are watching the creative endeavor of another person. The myths of realism and objectivity that are still so closely and erroneously attached to documentary as a form are cast aside here, to great effect. For what, after all, is art without subjectivity?

Mistaken for Strangers is nominally a film about indie band The National, who are so popular by this point that they will be kicking off their summer tour in support of their new record, Trouble Will Find Me, not at the United Palace or the Bowery Ballroom but instead at the Barclays Center. When Berninger asks his brother Matt, who is the band’s front man, how famous he considers himself, he tells him, “Not very famous.” “You’re more famous than any of my friends,” Berninger counters, and there we have the premise of the film in a nutshell.

For Mistaken for Strangers is not really about The National, or about what it’s like to be on tour with a rock band, but about brotherhood. Matt invited Tom along on their last tour, in support of High Violet, the album that crossed them over into the mainstream; Tom was supposed to work as the assistant tour manager, a position he ultimately lost as a result of being much more interested in taking video of the band and the shows than actually doing his job. Tom and his brother seem to have little in common, at least on the surface: Tom is a metal-head, still living at home, and seemingly without ambition except in a grand, abstract sense; Matt worked and worked and worked for years to ultimately wind up heading one of the most successful indie bands in the world. It is unsurprising that Matt seems a little resentful of his brother’s success, not in a mean-spirited way, but with a simple kind of longing to have a little of what he thus far feels he has been denied.

Something of this yearning certainly powers the film, which is really a movie about Tom making a movie about The National. Some may criticize this as childish or narcissistic, and it is, but harmlessly: the film’s childish instincts are levied with enough self-awareness on Berninger’s part that it never seems overly self-indulgent. It works, ultimately, because even saying it is a movie about Tom is not quite accurate: at its core, hidden away under jokes and concert sequences and solipsism, it is a love letter from Tom to Matt, a cry from a boy to the older brother he idolized and whom he is clearly still desperate to please. Matt Berninger is not painted as any kind of saint — Tom prods other band members into talking about instances of Matt losing his temper, which is apparently quite a sight to behold — but he is painted with a kind of fervent love that is deeply touching. It is this raw emotion that anchors the film in the real, that makes it not about a band or even music at all but about something we can all identify with and understand.

Stories We Tell is a deeper and more accomplished film than Mistaken for Strangers, though this should be taken not as a criticism of the latter but merely as a testament to the extraordinary achievement of the former. Sarah Polley, well-known as an actress and (at least among indie film circles) as the writer-director of Away From Her and, more recently, Take This Waltz, was given a grant by the Canadian government to make a film about her family, which she did on and off over the course of five years (during which time she also made Take This Waltz).

The film is composed of interviews with all her surviving family members, a small amount of archival footage from her childhood, and a considerably larger portion of staged archival footage that so closely mimics the real thing that I was not sure whether or not it was real until very late in the film. (Despite the film explicitly addressing this, several people in the audience at the screening I attended, at New Directors/New Films, remained under the impression that all of the “old” footage had been authentic.) Polley’s mother died when she was eleven, and the scratched, silent images of her (and her double) haunt the film, as does the absent woman herself: neither of her two marriages — to a first husband and to Polley’s father — was particularly happy, and her untimely death left her children and husband in the lurch – particularly Polley, who was a late-in-life baby and the only one still living at home in the direct wake of her mother’s death.

Without giving too much away, the film’s subjects — that is, Polley’s family members and family friends — all give their own impressions of Diane Polley, and the film attempts to wed these narratives together while simultaneously pointing out the ways they inevitably differ. All of the children saw their mother in a slightly different light, as did her husband and her friends: the ultimate, melancholy conclusion of the film is that there is simply no way for those still living to know what Diane really thought about her life, no way for them to know who she really was. She is a memory now, endlessly changeable and still incredibly powerful for all that she has fractured and faded with the passage of time. Even the images we see of her onscreen, that seem so real, that seem to at least have documented some fractional part of her existence, are for the most part just as imaginary as the stories her children tell about her so many years after her death.

At the question and answer session after the screening, Polley insisted that the movie was all about showing the differences in the stories we tell ourselves, about the fragile and formidable character of memory and about the importance of narrative in human existence. It is all of these things, but it is also something else, something considerably more personal: though we never hear from Polley herself — she appears, but does not interview herself, as it were — we get the sense that the film is as much an attempt to make the story of her mother’s life and death her own as Mistaken for Strangers is Tom Berninger’s attempt to insert himself into his brother’s story. Both Polley and Berninger have, ultimately, total control over the images they choose to show and the order in which they choose to show them; the universes they create within their films are theirs and theirs alone.

This does not mean that the movies are self-indulgent or un-self-critical, but it does mean that they represent a kind of desperate desire for selfhood, for presence, for acknowledgment — from the world at large but more specifically from their family members. The deepest melancholy in Stories We Tell is that, unlike Mistaken for Strangers, it is ultimately a love letter to a woman who will never see it, who can never come back. At the screening, Polley admitted a little shamefacedly that she realized that her first two films were also, in some way, attempts to understand her mother — though explaining how exactly this is true would be to give away too much of Stories We Tell, let me just say that she hit that nail on the head.

And for all the self-reflexive concerns of both of these movies — particularly Stories We Tell, which is, as I’ve written, the more formally ambitious of the two — this is what really powers them: the expression of a deep pain that is inextricable from love that is messy and difficult and profound. In this respect, these films feel in some ways more like works of fiction than documentaries — for what is fiction, after all, besides the expression of pain? As Bruce Springsteen told David Remnick when he was profiling him for the New Yorker, “T-Bone Burnett said that rock and roll is all about ‘Daaaaddy!’ It’s one embarrassing scream of ‘Daaaaddy!’ It’s just fathers and sons, and you’re out there proving something to somebody in the most intense way possible.” Modified a little, that could be applied to all artists in any medium, though the screams don’t have to be embarrassing. Berninger’s and Polley’s certainly are not.